CFD DEPARTMENT

CFD ANALYSIS ON AERODYNAMIC BEHAVIOUR FOR A FLAPPING WING TO UAV APPLICATION

 

Flapping wing UAVs

The main feature of the Unmanned Aerial Vehicles is the possibility to control them remotely or even program them and let them act without the human presence.  Their  use  is  particularly  well fitted  in  dangerous  places or  operations;  not  only  in  military  missions  in  war  sceneries,  but  also civil tasks in chemically or radioactively compromised areas. Especially in the first case, the model appearance and dynamics have to be as close as possible to an actual bird, according to the place of use and local distribution of certain species of animal. Since  this  type  of  robots  are  the  most technologically developed  so  far,  they  are  supplied  with  complicated  mechanical  train  able  to reproduce the flapping motion of the wing considering many of the joints of a real bird wing.  The large field  of  application  justifies  fluid  dynamics  and  aerodynamics  studies in  order  to  have realistic simulations before the actual manufacturing of the prototypes. Since, our project mainly concentrated on flow behaviour over on Flapping wing by using CFD.

Geometry:

Wing Configuration:

• Rectangular

• Tapper

• Swept wing

Aerofoil Used:

• E452

• Selig 1020

• Selig 1223

 

User Defined Function:

The  so  called UDFs  are  the  programming  codes  which have  the role to  control  to  motion  of  the moving surfaces. They are usually written in C language and they need some reference points into the mesh. For this reason, all the reference systems of the CAD drawing, the solid model and the mesh have to match on the same point.  This  type  of UDF is  generally  fitted  to  include motions about  three  different axes: roll,    and pitch.  The frequency of the flapping is another variable which can be adjusted as preferred.  However, this program is suited to move a rigid wing.

 

Analysis Description:

CFD simulations were first carried out for the Aerofoil E472 wing using ANSYS Fluent 15 solver with k-ε turbulence model at Velocity 12 m/s, Flapping Amplitude 60, Feathering Amplitude 30 and Frequency 20 Hz. The simulations were then carried out on the different wing configurations for various Aerofoils like Selig 1020 and Selig 1223. In this flight condition, strong turbulence builds around the wing. The pressure coefficient (CP), Lift coefficient (CL) and Drag coefficient (CD) were extracted for all configurations.

 

 

Fig2. Result Comparison

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 3. Stream lne contour shows that absence of wing tip vortices in Selig 1223 wing Tip

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Result:

The result from all configuration compared and finally Tapper wing and Swept configuration selected for final analysis. The above graph shows that comparison between Tapper wing and Swept wing configuration. The mean CL and CD value for Swept wing is 1.8 and 0.7 respectively. The CL value of Swept is 33% more than tapper wing configuration and CD value is 17% less than tapper wing configuration. This because of the Selig 1223 Swept wing have less turbulence and wing tip vortices controlled by Eagle wing shape.  The finally result concluded that the Swept wing configuration give best aerodynamic performance for Flapping wing motion.